1. Technical Field
The present invention relates to an electrically heated window with a resistance heating element, and more specifically to a window with a resistance heating element which is arranged to be in working cooperation with an imaging device such as a camera.
2. Background
As road safety bodies, government agencies, vehicle manufacturers and other interested parties strive to increase road safety, despite increasing congestion and the proliferation of potential distractions to drivers, one approach adopted is to provide technical aids to drivers to assist them to drive safely. For example, one such aid may monitor a vehicle's course relative to the road ahead, and alert the driver when deviations occur. It is also possible to monitor the separation between one vehicle and the next, and alert the driver when the separation drops below a desired value. In more advanced systems, it is possible to arrange for the vehicle to take remedial action, such as braking, automatically. A further possibility is to provide assistance to the driver in conditions of poor visibility due to adverse weather or low light levels, e.g. in fog or at night. It is also desirable to assist the driver to maneuver the vehicle without incident by using cameras to augment the driver's vision in areas where it is difficult for the driver to see, e.g. immediately around the vehicle below the level of the windows, especially to the sides or rear of the vehicle.
All such systems rely on some type of imaging device, for example a camera, to view or monitor the vehicle's surroundings, be it the road itself, other vehicles, etc. It is self-evident that the functioning of such systems will be adversely affected if the image formed by the device is impaired in some way. Accordingly, one prerequisite is for the imaging device to have a clear view, free of condensation, frost, ice, moisture or snow on the window, regardless of weather conditions.
Patent publication of EP 1,605,729 A2 teaches a double-paned window that may be used in a vehicle such as a car. The document further describes the use of an imaging device. To prevent the imaging device from being obstructed by ice or moisture window, a conducting heating element is laminated between the two panes of the window. The conducting element disclosed comprises thin tungsten wires which are typically 15-50 μm thick and arranged 1.8-3.0 mm apart. The tungsten wires can be arranged along a path which may be crimped. However crimped wires or wires with a meander form have been found to glare, i.e. to provide multiple points of unwanted reflections that interfere with the imaging device especially during sunny weather. Hence these forms provide drawbacks for sensitive imaging devices. This problem becomes readily apparent when such imaging devices are arranged to feed digital signals to processing units such as computers, which are to read and analyze the captured image(s).
The described wires may further be arranged in a boustrophedon pattern, i.e. straight, parallel lines connected to one another and extending in alternating directions. However for sensitive imaging devices and the connected analysis devices, these kinds of patterns can cause interference with the readings of the imaging device and the interpretation of the captured image(s), for instance when imaging specific parameters such as the center line of the road or the horizon. It therefore remains to provide a solution which provides both a reduced tendency to glare and which minimizes the risk of interference with sensitive imaging devices and related analyzing equipment.